The present invention relates generally to visual guidance systems and, more particularly, to visual guidance systems used to facilitate mating of a refueling boom on a tanker aircraft with a boom receptacle on a receiving aircraft to enable inflight refueling of the receiving aircraft.
Inflight aircraft refueling operations utilizing the boom system presents numerous difficulties for the boom operator. In refueling operations utilizing the boom system, the tanker aircraft is flown in a level flight path while the receiver aircraft is flown into a desired position to enable proper mating of the aircraft boom and receiver aircraft receptacle. The boom is swivably mounted to the tanker aircraft and is telescopically extendable to refueling structures require the boom operator to have a good view of both the refueling structures and the aircraft. Both indirect and direct viewing of the orientation and range of the aircraft refueling structures utilized in the refueling operations may often take place under adverse viewing conditions such as a low contrast/high glare environment which may be due to a bright undercast. Under such conditions, visual cues may be distorted resulting in errors in depth perception.
Some prior art direct viewing systems require the boom operator to lie prone in the rear of the tanker aircraft where he has a direct out-the-window view of the boom and receiver aircraft. However, refueling operations in such a prone position are very fatiguing to the boom operator. In addition to being required to frequently perform these operations under adverse environment conditions, the operators view through the window is very limited.
Some prior art indirect viewing systems utilize 3-D glasses to provide depth cues. Use of these glasses is associated with eye fatigue, frequent loss of steropsis i.e., loss of fusion and 3-D perception, and a phenomena known as pseudomovement i.e., the perceived shifting of the visual field in nonlinear fashion with incremental head motion. An example of such a system is disclosed in U.S. Pat. No. 4,298,176 to Kendall.
Some prior art systems have been designed which utilize nuclear radiation source and detection equipment in the tanker and receiver aircraft to enable the boom operator to perform the link up operations without a direct or indirect view of the refueling structures or aircraft. An example of such a system is disclosed in U.S. Pat. No. 3,285,544 to Chope et al. The Chope system utilizes a cobalt or other radiation source in the tanker aircraft and nuclear detection equipment in the receiver aircraft. The direction sensitive detector equipment provides azimuth, elevation and range information by means of an oscillographic display. A primary disadvantage of this type of system is the difficulty faced by the operator in using dot representations on a screen to guide the aircraft and refueling structures into the desired mating position.
Other prior art systems use optical systems to determine the location and range of the receiver aircraft relative to the tanker aircraft and the boom. Examples of such systems are disclosed in U.S. Pat. Nos. 4,025,193 and 3,917,196 both to Pond et al. The Pond systems use an optical source on the tanker aircraft to transmit a light beam which is reflected by suitably positioned reflectors on the receiver aircraft and the boom. An optical sensor on the tanker aircraft determines azimuth, elevation and range of the receiver aircraft and the boom and feeds this information to a computer and to a cathode ray tube rectangular coordinate display. The relative positions are thus displayed as dots on a screen. Consequently, as with the Chope system, the Pond systems have the disadvantage of being very difficult to effectively use because they do not provide a realistic depiction of the aircraft and structures thereof used in refueling link up operations.
Other prior art systems use an optical array on one aircraft to communicate relative motion, range and position to the pilot of the other aircraft. An example of such a system is disclosed in U.S. Pat. No. 4,158,885 to Neuberger. The Neuberger system incorporates panels of lights mounted on the underbelly of the tanker aircraft. The lights are selectively illuminated and/or strobed to signal to the pilot of the receiver aircraft the fore-aft, up-down and right-left position as well as the fore-aft rate of the two aircraft. A primary disadvantage with these systems is that pilot instructions given by such light signals are difficult to follow with any high degree of precision. In addition, there is significant chance of pilot error in interpreting the light signals which can potentially result in a collision. Furthermore, such a system does not aid the boom operator in mating the boom with the boom receptacle.
A guidance system is thus needed that can provide the pilot and boom operator with a realistic, real time depiction of the refueling structures and aircraft. A guidance system is also needed that provides a high degree of precision in link up of refueling aircraft while being easy to use and allowing minimal chance of error.